Smooth-Operating Servos Usher in a Stamping Renaissance Period

Acro stamps these parts for the iconic barber’s jar of combs on a 110-ton servo press. It was able to reshore the job from China thanks to the ability of the servo press to draw and form the prepolished stainless steel without affecting its surface finish. Under previous production methods on a conventional press, the stamped parts required a secondary hand-finishing process.

The last five years for Milwaukee, WI metalformer Acro Metal Stamping have been a renaissance period. The company has “reinvented” itself to emerge from the industry downturn and recover from a Chinese invasion of its customer base. So says Acro president Jim Wolfenberg, who admits that from 2005 to 2008, Acro lost 20 to 25 percent of its book of business to China. Add recessionary pressure during that time and “we needed to reinvent the company,” Wolfenberg admits.

Before its renaissance, Acro’s custom-stamping business centered on a fleet of 20 to 25 conventional mechanical presses from 32 to 150 tons, with bed size to 27 by 53 in. In 2010 its pressroom makeover kicked off with the acquisition of a pair of Komatsu servo presses —a 110-ton and a 200-ton model. Two more servo presses landed in 2011, 60- and 80-ton models. Finally, early in 2013 Acro added another 200-ton Komatsu servo press and a 60-ton servo press.

“Some 50 percent of our production now runs through the six servo presses,” says Wolfenberg, noting that the productivity gains realized have allowed him to decommission several of his conventional mechanical presses. “The capabilities of the servo presses have allowed us to expand our footprint into our traditional key markets, such as electronics and electric motors, while bringing an entirely new set of customers to our door.”

New Capabilities, New Jobs

Wolfenberg credits his servo-press stable with attracting a set of “more complex stamping jobs” that ultimately account for as much as 20 percent of the firm’s business. “And, I’d say we’ve increased our ability to quote a wider variety of jobs—and reduced no-quote jobs—by as much as 60 percent, thanks to the servo presses.”

Asked to elaborate, Wolfenberg credits the flexibility and stroke control that comes with servo-press technology with Acro’s ability to add deep drawing of stainless steel to its resume. Case in point: stamping parts for the iconic comb container found in nearly every barber shop and hair solon. To form the top cover of the container, Acro’s 110-ton servo press performs a nearly 2-in. draw on a 4-in.-dia. blank of 0.012-in. stainless steel. The press also forms the stainless-steel strainer that sits inside the comb container. Both jobs had previously been offshored to China, and Wolfenberg is understandably quite proud to have reshored the work.

“We can draw the cover in one operation in the servo press,” he notes, “impossible to do in a conventional mechanical press and much faster than if we were to run them in a hydraulic press.”

Acro was able to reshore the job thanks to the ability of the servo press to draw and form the prepolished stainless steel without affecting its surface finish. Under previous production methods on a conventional press, the stamped parts required a costly and time-consuming secondary hand-finishing process.

Cam-Actuated Operations, and Coining

Other additions to Acro’s resume, thanks to servo-press capabilities, include increased ability to perform in-die tapping, cam-actuated operations and coining.

“When tapping, with the servo press, we can actuate the tapping operation at any point in the stroke, and control ram speed,” Wolfenberg says. “With a conventional press we only can tap during one portion of the stroke. We have much more flexibility in our process now.

“When coining,” Wolfenberg continues, “we’ve been able to reduce 3⁄16-in. material to 3⁄32 in.—typically, the tool would just bounce in a conventional press. And, we’ve found that the ability of the servo press to slow or even pause mid-stroke allows cam-actuated forming during the stroke. We can bring a horn into the die, come down around it and retract the horn, all in one stroke, eliminating a secondary operation.”

Acro performs this operation routinely to form a J-shaped bracket. Wolfenberg explains: “The die is designed to form two 90-deg. bends, in separate planes. Typically each bend would require a separate press operation. In the servo press, we form the first 90-deg. bend, and then use an air cylinder to help make the second bend. We then retract the cylinder and kick out the part—all in one stroke.”

Diminished Die Maintenance

The ability to perform more work per press stroke also has allowed Acro to simplify its tooling and eliminate stations from the complex progressive dies it designs and builds. “We’re typically taking four- to five-station dies down to two or three stations,” says Acro toolroom supervisor Jim Wobig. Wobig quickly credits the firm’s move in 2010 to 3D die design (LOGOPRESS3) with helping the company leverage the flexibility of its servo presses.

At the back end, Wobig also notes that die-maintenance costs have dropped dramatically when dies previously run in the firm’s conventional mechanical presses move over to the servo presses. Some of the firm’s dies are more than 50 years old, used to stamp high volumes of electrical parts (500,000 or more) such as connectors and terminals. Says Wobig: “We’d often experience significant burr issues with these dies, and after a while we’d have trouble holding dimensional accuracy.”

Those problems caused dies to route to the toolroom for 4 to 5 hr. of maintenance after every run. “With the added control over stroke rate and position,” says Wobig, “we’re now able to use those older dies for at least two production runs, or 1 million stamped parts, before they require maintenance. And, the maintenance required is much less intensive, requiring only about 2 hr. in the toolroom.” MF